This invention relates to an air drag reduction apparatus for a tractor-trailer vehicle, and more particularly to a drag reduction apparatus automatically deployable to an operative position only at a predetermined high speed of the vehicle.
Air drag reduction apparatuses for tractor-trailer vehicles of various types are known in the art. Examples of some of these drag reduction apparatuses are disclosed in the Saunders U.S. Pat. Nos. 3,241,876; 3,309,131; 3,348,873 and 3,697,120; the Stamm U.S. Pat. No. 2,863,695 and the DeVaughn U.S. Pat. No. 3,425,740.
The above patents disclose air drag reducing devices mounted on the trailer, or the tractor and the trailer, for reducing the drag created in the air gap between the tractor and the trailer. These prior apparatus are rigid structures. Those devices, such as DeVaughn's, which extend the full length of the air gap sacrifice the ability of the tractor to turn, particularly at low speeds. The other devices such as Stamm's or Saunders are fixed with respect to the vehicle and attempt to keep the air gap between the tractor and trailer sufficiently clear to allow the tractor and trailer to turn with respect to each other without interference while reducing the air drag associated with the air gap. Such devices attempt to reduce the air drag by creating an air vortex in the air gap that acts as a fluid fairing to deflect the air flow about the vehicle over the air gap. The primary problems associated with these devices are the difficulty associated with maintaining the vortex, especially for the longer air gaps and for normally encountered cross winds, and the air drag associated with the vortex and the air flowing thereby.
Of the drag reduction apparatuses for tractor-trailer vehicles, or for any other type land vehicles, known to the applicant, none are capable of moving between a stowed position where the apparatus does not interfere with the maneuverability of the vehicle and an operative deployed position automatically, much less being automatically deployed by the wind forces at higher speeds of the vehicle.